Exploration and Confirmation of the Indole-3-Acetic Acid Biosynthetic Pathway in Plant Growth-Promoting Rhizobacteria Priestia megaterium W101

The growing global demand for food is limited by low seed germination rates, a key constraint in crop production. Priestia megaterium W101, a plant growth-promoting rhizobacterium with high indole-3-acetic acid (IAA) yield, was found to significantly promote the germination of wheat seeds and the growth of the root system. For the first time, we characterized in Priestia megaterium a complete indole-3-pyruvic acid (IPyA) pathway, encoded by ipdC, patB, feaB, and gene1566, together with a yedL-encoded alternative pathway, through integrated multiomics analyses and CRISPR/Cas9-mediated heterologous expression. In addition, we reconstructed the complete IPyA pathway in Bacillus subtilis 168, which increased IAA production by approximately 98% compared to that in the wild-type strain. Overall, this study elucidates the IAA biosynthetic network in W101 and highlights its potential as a core strain for sustainable microbial inoculant development in green agriculture.